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Clinical data | |
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Trade names | Enovid, Norinyl, Ortho-Novum, others |
Other names | Ethinylestradiol 3-methyl ether; EEME; EE3ME; CB-8027; L-33355; RS-1044; 17α-Ethynylestradiol 3-methyl ether; 17α-Ethynyl-3-methoxyestra-1,3,5(10)-trien-17β-ol; 3-Methoxy-19-norpregna-1,3,5(10)-trien-20-yn-17β-ol |
AHFS/Drugs.com | International Drug Names |
MedlinePlus | a601050 |
Routes of administration | By mouth[1] |
Drug class | Estrogen; Estrogen ether |
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Pharmacokinetic data | |
Metabolites | Ethinylestradiol |
Elimination half-life | Mestranol: 50 min[2] EE: 7–36 hours[3][4][5][6] |
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ECHA InfoCard | 100.000.707 |
Chemical and physical data | |
Formula | C21H26O2 |
Molar mass | 310.437 g·mol−1 |
3D model (JSmol) | |
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Mestranol, sold under the brand names Enovid, Norinyl, and Ortho-Novum among others, is an estrogen medication which has been used in birth control pills, menopausal hormone therapy, and the treatment of menstrual disorders.[1][7][8][9] It is formulated in combination with a progestin and is not available alone.[9] It is taken by mouth.[1]
Side effects of mestranol include nausea, breast tension, edema, and breakthrough bleeding among others.[10] It is an estrogen, or an agonist of the estrogen receptors, the biological target of estrogens like estradiol.[11] Mestranol is a prodrug of ethinylestradiol in the body.[11]
Mestranol was discovered in 1956 and was introduced for medical use in 1957.[12][13] It was the estrogen component in the first birth control pill.[12][13] In 1969, mestranol was replaced by ethinylestradiol in most birth control pills, although mestranol continues to be used in a few birth control pills even today.[14][9] Mestranol remains available only in a few countries, including the United States, United Kingdom, Japan, and Chile.[9]
Mestranol was employed as the estrogen component in many of the first oral contraceptives, such as mestranol/noretynodrel (brand name Enovid) and mestranol/norethisterone (brand names Ortho-Novum, Norinyl), and is still in use today.[7][8][9] In addition to its use as an oral contraceptive, mestranol has been used as a component of menopausal hormone therapy for the treatment of menopausal symptoms.[1]
See also: Ethinylestradiol § Side effects, and Estrogen (medication) § Side effects |
Mestranol is a biologically inactive prodrug of ethinylestradiol to which it is demethylated in the liver (via O-Dealkylation) with a conversion efficiency of 70% (50 μg of mestranol is pharmacokinetically bioequivalent to 35 μg of ethinylestradiol).[15][16][11] It has been found to possess 0.1 to 2.3% of the relative binding affinity of estradiol (100%) for the estrogen receptor, compared to 75 to 190% for ethinylestradiol.[17][18]
The elimination half-life of mestranol has been reported to be 50 minutes.[2] The elimination half-life of the active form of mestranol, ethinylestradiol, is 7 to 36 hours.[3][4][5][6]
The effective ovulation-inhibiting dosage of mestranol has been studied in women.[19][20][21] It has been reported to be about 98% effective at inhibiting ovulation at a dosage of 75 or 80 μg/day.[22][21][23] In another study, the ovulation rate was 15.4% at 50 μg/day, 5.7% at 80 μg/day, and 1.1% at 100 μg/day.[24]
Estrogen | Other names | RBA (%)a | REP (%)b | |||
---|---|---|---|---|---|---|
ER | ERα | ERβ | ||||
Estradiol | E2 | 100 | 100 | 100 | ||
Estradiol 3-sulfate | E2S; E2-3S | ? | 0.02 | 0.04 | ||
Estradiol 3-glucuronide | E2-3G | ? | 0.02 | 0.09 | ||
Estradiol 17β-glucuronide | E2-17G | ? | 0.002 | 0.0002 | ||
Estradiol benzoate | EB; Estradiol 3-benzoate | 10 | 1.1 | 0.52 | ||
Estradiol 17β-acetate | E2-17A | 31–45 | 24 | ? | ||
Estradiol diacetate | EDA; Estradiol 3,17β-diacetate | ? | 0.79 | ? | ||
Estradiol propionate | EP; Estradiol 17β-propionate | 19–26 | 2.6 | ? | ||
Estradiol valerate | EV; Estradiol 17β-valerate | 2–11 | 0.04–21 | ? | ||
Estradiol cypionate | EC; Estradiol 17β-cypionate | ?c | 4.0 | ? | ||
Estradiol palmitate | Estradiol 17β-palmitate | 0 | ? | ? | ||
Estradiol stearate | Estradiol 17β-stearate | 0 | ? | ? | ||
Estrone | E1; 17-Ketoestradiol | 11 | 5.3–38 | 14 | ||
Estrone sulfate | E1S; Estrone 3-sulfate | 2 | 0.004 | 0.002 | ||
Estrone glucuronide | E1G; Estrone 3-glucuronide | ? | <0.001 | 0.0006 | ||
Ethinylestradiol | EE; 17α-Ethynylestradiol | 100 | 17–150 | 129 | ||
Mestranol | EE 3-methyl ether | 1 | 1.3–8.2 | 0.16 | ||
Quinestrol | EE 3-cyclopentyl ether | ? | 0.37 | ? | ||
Footnotes: a = Relative binding affinities (RBAs) were determined via in-vitro displacement of labeled estradiol from estrogen receptors (ERs) generally of rodent uterine cytosol. Estrogen esters are variably hydrolyzed into estrogens in these systems (shorter ester chain length -> greater rate of hydrolysis) and the ER RBAs of the esters decrease strongly when hydrolysis is prevented. b = Relative estrogenic potencies (REPs) were calculated from half-maximal effective concentrations (EC50) that were determined via in-vitro β‐galactosidase (β-gal) and green fluorescent protein (GFP) production assays in yeast expressing human ERα and human ERβ. Both mammalian cells and yeast have the capacity to hydrolyze estrogen esters. c = The affinities of estradiol cypionate for the ERs are similar to those of estradiol valerate and estradiol benzoate (figure). Sources: See template page. |
Compound | Dosage for specific uses (mg usually)[a] | ||||||
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ETD[b] | EPD[b] | MSD[b] | MSD[c] | OID[c] | TSD[c] | ||
Estradiol (non-micronized) | 30 | ≥120–300 | 120 | 6 | - | - | |
Estradiol (micronized) | 6–12 | 60–80 | 14–42 | 1–2 | >5 | >8 | |
Estradiol valerate | 6–12 | 60–80 | 14–42 | 1–2 | - | >8 | |
Estradiol benzoate | - | 60–140 | - | - | - | - | |
Estriol | ≥20 | 120–150[d] | 28–126 | 1–6 | >5 | - | |
Estriol succinate | - | 140–150[d] | 28–126 | 2–6 | - | - | |
Estrone sulfate | 12 | 60 | 42 | 2 | - | - | |
Conjugated estrogens | 5–12 | 60–80 | 8.4–25 | 0.625–1.25 | >3.75 | 7.5 | |
Ethinylestradiol | 200 μg | 1–2 | 280 μg | 20–40 μg | 100 μg | 100 μg | |
Mestranol | 300 μg | 1.5–3.0 | 300–600 μg | 25–30 μg | >80 μg | - | |
Quinestrol | 300 μg | 2–4 | 500 μg | 25–50 μg | - | - | |
Methylestradiol | - | 2 | - | - | - | - | |
Diethylstilbestrol | 2.5 | 20–30 | 11 | 0.5–2.0 | >5 | 3 | |
DES dipropionate | - | 15–30 | - | - | - | - | |
Dienestrol | 5 | 30–40 | 42 | 0.5–4.0 | - | - | |
Dienestrol diacetate | 3–5 | 30–60 | - | - | - | - | |
Hexestrol | - | 70–110 | - | - | - | - | |
Chlorotrianisene | - | >100 | - | - | >48 | - | |
Methallenestril | - | 400 | - | - | - | - | |
See also: List of estrogens and List of estrogen esters § Ethers of steroidal estrogens |
Mestranol, also known as ethinylestradiol 3-methyl ether (EEME) or as 17α-ethynyl-3-methoxyestra-1,3,5(10)-trien-17β-ol, is a synthetic estrane steroid and a derivative of estradiol.[44][45][46] It is specifically a derivative of ethinylestradiol (17α-ethynylestradiol) with a methyl ether at the C3 position.[44][45]
In April 1956, noretynodrel was investigated, in Puerto Rico, in the first large-scale clinical trial of a progestogen as an oral contraceptive.[12][13] The trial was conducted in Puerto Rico due to the high birth rate in the country and concerns of moral censure in the United States.[47] It was discovered early into the study that the initial chemical syntheses of noretynodrel had been contaminated with small amounts (1–2%) of the 3-methyl ether of ethinylestradiol (noretynodrel having been synthesized from ethinylestradiol).[12][13] When this impurity was removed, higher rates of breakthrough bleeding occurred.[12][13] As a result, mestranol, that same year (1956),[48] was developed and serendipitously identified as a very potent synthetic estrogen (and eventually as a prodrug of ethinylestradiol), given its name, and added back to the formulation.[12][13] This resulted in Enovid by G. D. Searle & Company, the first oral contraceptive and a combination of 9.85 mg noretynodrel and 150 μg mestranol per pill.[12][13]
Around 1969, mestranol was replaced by ethinylestradiol in most combined oral contraceptives due to widespread panic about the recently uncovered increased risk of venous thromboembolism with estrogen-containing oral contraceptives.[14] The rationale was that ethinylestradiol was approximately twice as potent by weight as mestranol and hence that the dose could be halved, which it was thought might result in a lower incidence of venous thromboembolism.[14] Whether this actually did result in a lower incidence of venous thromboembolism has never been assessed.[14]
Mestranol is the generic name of the drug and its INN , USAN , USP , BAN , DCF , and JAN , while mestranolo is its DCIT .[44][45][1][9]
Mestranol has been marketed under a variety of brand names, mostly or exclusively in combination with progestins, including Devocin, Enavid, Enovid, Femigen, Mestranol, Norbiogest, Ortho-Novin, Ortho-Novum, Ovastol, and Tranel among others.[7][44][49][45] Today, it continues to be sold in combination with progestins under brand names including Lutedion, Necon, Norinyl, Ortho-Novum, and Sophia.[9]
Mestranol remains available only in the United States, the United Kingdom, Japan, and Chile.[9] It is only marketed in combination with progestins, such as norethisterone.[9]
Mestranol has been studied as a male contraceptive and was found to be highly effective.[50][51][52][53] At a dosage of 0.45 mg/day, it suppressed gonadotropin levels, reduced sperm count to zero within 4 to 6 weeks, and decreased libido, erectile function, and testicular size.[50][51][53][52] Gynecomastia occurred in all of the men.[50][51][53][52] These findings contributed to the conclusion that estrogens would be unacceptable as contraceptives for men.[51]
In 2021, mestranol was one of the 12 compounds identified in sludge samples taken from 12 wastewater treatment plants in California that were collectively associated with estrogenic activity in in vitro. [54]